As parliamentary theatre goes, this was as good as it gets — the prosecution of Parliament's prosecutor-in-chief.

It is extremely rare for an opposition leader to be hauled before a parliamentary committee, but Conservatives and Liberals sought to have their way with NDP Leader Tom Mulcair during a two-hour interrogation on Thursday.

At issue was an alleged spending irregularity in which NDP staffers — paid by taxpayers — were engaged in partisan activity in a Montreal satellite office. But the day's proceedings revealed much more about how this Parliament operates than it did about any NDP malfeasance.

Yes, rules are rules, and it would appear that New Democrats may have embraced the Ottawa modus operandi of bending, pushing and muddying — although Mulcair steadfastly denied that for two hours.

Anyone who still believes New Democrats splash around in some chaste pool in Ottawa, while the other parties truck through the muck, hasn't been paying attention.

These alleged transgressions are not to be ignored, but neither should they be inflated. No one need await a 2015 federal election campaign hanging on jobs, prosperity and the NDP's satellite offices.

Of much more importance to Canadian voters was the demeanour of a man who would be prime minister, a man who has assiduously worked to sand his sharp edges since assuming the NDP leadership. Mulcair's political Achilles heel has been the perception of a prickly, impatient man, who is quick to anger.

Conservatives clearly relished an opportunity for payback, having sat on their hands for months while Mulcair kept Prime Minister Stephen Harper on the defensive.

There was no eruption of Mount Mulcair on Thursday.

He kept his cool, but he showed contempt for his inquisitors, and arrogance crept into his answers. Although, if you were an NDP supporter, you would say your man ceded no ground, and gave back better than he got.

Mulcair used his opening statement to attack Harper's Conservatives and Justin Trudeau's Liberals; he used questions from his MPs to publicize budget cuts to his office and make partisan claims; and he even leavened the morning with a bit of humour, twice remarking, "Oh, darn" when time ran out for someone questioning him.

But it was his encounters with Conservative tormenter, Kitchener Centre MP Stephen Woodworth — heretofore best known here for his efforts to reopen the abortion debate — that came permanently marinated in sarcasm.

Mulcair tried to tutor Woodworth on law, going mano-a-mano with him in Latin, and suggesting Woodworth provide his address so the NDP could pay him some legal fees for making its case.

At another point, the two got down in the weeds in debate, only to have Mulcair tell the Conservative he was discussing a point laid out in the bibliography on the drafting and interpretation of legislative texts.

"I am the author,'' Mulcair said. "I would be happy to give you an autographed copy.''

Woodworth started his line of questioning by saying that Mulcair liked questions that could be answered “yes or no” — a reference to the missiles Mulcair had fired at Harper over the months.

Mulcair readily agreed, then took off as if he was trying to filibuster for two hours.

The NDP leader has often been freighted with the swagger of a man who thinks he is the smartest in the room, but his party has also taken succour in the belief he can hold his own against anyone — a trait which will serve him well in next year's campaign, particularly in the debates.

The temper has never surfaced since he won the leadership in the spring of 2012 — not when he was taunted daily on his views on energy extraction, not when he was caught running a stop sign on Parliament Hill, and not when he grappled with party defections.

He deflected and counterattacked with aplomb on Thursday. If this was a preview of Mulcair as a man under attack in an election campaign, this was ultimately more revealing than anything we learned about his satellite offices.

Tim Harper is a national affairs writer with Torstar Syndication Services.